The polymerization of chloroprene in aqueous alkaline emulsion in the presence of emulsifying agents is well known. Depending on the ultimate use of the polychloroprene, diverse formulations have been proposed (e.g. use of dissolved sulphur, use of a chain transfer agent, addition of a peptizing agent and the like) which make it possible to obtain diverse types of rubber within a specific viscosity range. See, for example, U.S. Pat. Nos. 3,808,183; 3,872,043; 3,984,609 and 3,899,459.
A main processing obstacle encountered by manufacturers resides in the difficulty of obtaining a product viscosity which remains at a constant value from the time when the polymerization reaction has ended to the time when the polymer is isolated from the latex. This period is generally between 10 and 100 hours. In a general way, the viscosity tends to increase during storage. This phenomenon, known as "latex ageing," is due to a crosslinking which is more or less rapid depending on the operating conditions. The increase in the viscosity may or may not be accompanied by the appearance of a gel which results in the polychloroprene becoming partially insoluble in formulations for adhesives and in a perceptible modification of the physical and rheological properties of the polymers.
An improved process for the polymerization of chloroprene in the presence of mercaptans, according to which an hydrophilic amide containing hydroxyl groups is added to the reaction medium has recently been proposed (U.S. Pat. application Ser. No. B 468 198, now U.S. Pat. No. 3,925,340). The object of the addition of the amide is to increase the degree of conversion of the monomer into the polymer without the formation of a gel.